Disable the white light when shooting a picture

When I take pictures with flash disabled, the camera still lights up a white light (on the right near the shutter button)
Why is this, and how can it be disabled ?

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Isn't that a focus assist light...Why would you not want it operating...

As Pedro mentioned, it's the autofocus assist light. You can disable it in the menus, but be aware that in some lighting conditions where you wouldn't necessarily use flash it still helps with the autofocus function, so don't be surprised if your camera starts hunting for focus in those situations.